Bob Baffert began his career as a jockey. As he grew bigger, he had difficulty maintaining the required jockey weight, (around 100-108 pounds), and he switched to the training of American Quarter Horses. In 1991, he began devoting himself to conditioning Thoroughbreds for flat racing. From a base in California, he became the United States' leading money-winning trainer four times. He got his first big break in 1992 when he won his first Breeder's Cup race with Thirty Slews.